Hair Growth Cycle

February 7th, 2015
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To understand the hair growth cycle, you first need to understand the structure of a hair.

Hair Structure

Reach up and yank a hair out of your head. Carefully! You want the whole thing, not just broken hair. See the little knob at the end that was in your head? That's called the bulb. It sits down in the dermis – the second layer of skin – inside the follicle. The bulb is what keeps your hair anchored into your skin, and is what stimulates hair growth. The stem cells that create hair are in here, this is the only part of your hair that is actually alive. Right now, the cells left in the follicle are getting to work to construct another bulb and strand of hair!

(Before you ask, no, yanking out your gray hairs will not cause two more to grow in their place. One strand per follicle! It will grow back eventually, though, so you might as well just wait for it to fall out and renew on its own.)

The strand? It is called the shaft. It's made of 3 parts – the core, or medulla; the cortex, which wraps around the core and provides structure; and the cuticle, which consists of several layers of very thin cells that are laid out much like fish scales. The cuticle is meant to protect the other two layers.

All of your body hair has this structure, by the way. It's just easier to look at the structure using the terminal hairs of your head.

Hair Growth Cycle

Hair Growth Cycle

Now let's talk about the hair growth cycle. Hair grows in three phases, and all three phases are happening all over your body right now! What, seriously? YES! As each hair falls out, the hair growth cycle starts all over again. Since hair falls out individually, rather than all at once, some hair is just starting, some is in the middle of the cycle, and some is getting ready to stop growing and leave you.

Anagen Hairs

The first phase of the hair growth cycle is called the anagen phase. During this phase, the hair follicle burrows into the dermis to protect the sprouting hair and nourish the rapidly multiplying hair cells. The length of the anagen phase determines how long the hair will grow, usually between 2 and 6 years before the follicle stops producing cells and the hair falls out. How long the anagen phase lasts varies by individual, and is determined by your genetics. If Mom could grow her hair down to her hips, you probably can, too!  Between 80% and 85% of your hair is currently in the anagen phase.

Catagen Hairs

The second phase of the hair growth cycle is called the catagen phase. The catagen phase is a transitional period for the hair follicles. At any given time, about 1% of your hair is in the catagen phase. This is when cell production begins to wind down, and the follicle starts to shrink. As the follicle shrinks, it will detach from the dermis, which will cut off blood supply to the bulb, causing the bulb to shrink and eventually die. The catagen phase lasts around 2 weeks.

Telogen Hairs

The final phase of the hair growth cycle is the telogen phase. For hair, this is the end of the line. During the telogen phase, the hair follicle essentially hibernates for between 1 and 4 months. Like the anagen phase, the length of the telogen phase is determined by your genetics. The hair shaft does not immediately fall out, as skin cells surrounding it still continue to grow, giving it a little more time to stick around. At the end of this resting period, however, the follicle will wake up and begin burrowing back into the dermis to start all over again, which will soften the surrounding cells and push the hair strand out. The anagen phase will start again, a new strand will become visible in about two weeks. Roughly 15% of your hair is in the telogen phase right now, which accounts for the hair you find in your brush.

Your Electrologist Knows What To Do!

Since hair has different phases of growth, you may require multiple electrolysis sessions and multiple methods to achieve the results you want. This is especially true when treating larger areas, such as the legs and arms. Thankfully, your trained electrologist will know exactly what you need and when!

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3 Responses to “Hair Growth Cycle”

  1. Excellent description of the phases and cycles of hair growth to help explain WHY electrology treatments take a series of appointments to accomplish permanence.

    Thank you for providing this information to our consumers!

  2. Patricia says:

    Thank you! Sharing!

  3. Jane Curry says:

    Thanks for posting this, June. I have lost 50% of my hair since December. I found out it was a thyroid problem. It's slowly growing back. I loved learning about the whole hair growth process. Thank you for the education!

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